permeable wall

When I use N-S equation with LU-SGS scheme on the implicit side and MUSCL steger-warming splitting on the explicit side to calculate a blunt cone,I encounter a strange phenomenon:as for the Re>10000 and Mach=15,even with two temperature model nonequlibrium cheamic reaction,I yield the correct result.However,as for the Re=2275 and Mach=22.67 with iso-thermal wall in order to simulate the circumstance on the 70km high altitude,the streamlines give off from the wall so that the stand-off distance of shock wave is beyond the experimental data.It has taken me several weeks to examine the errors of my program but in vain.

Could anyone give me some useful suggestions?All comments are welcomed!